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Authors: Kato, M.
Saio, H.
Henze, M.
Ness, J-U.
Osborne, Julian P.
Page, Kim L.
Darnley, M. J.
Bode, M. F.
Shafter, A. W.
Hernanz, M.
Gehrels, N.
Kennea, J.
Hachisu, I.
First Published: 10-Oct-2016
Publisher: American Astronomical Society, IOP Publishing
Citation: The Astrophysical Journal 830:40 (12pp), 2016 October 10
Abstract: Models of nova outbursts suggest that an X-ray flash should occur just after hydrogen ignition. However, this X-ray flash has never been observationally confirmed. We present four theoretical light curves of the X-ray flash for two very massive white dwarfs (WDs) of 1.380 and 1.385 ${M}_{\odot }$ and for two recurrence periods of 0.5 and 1 yr. The duration of the X-ray flash is shorter for a more massive WD and for a longer recurrence period. The shortest duration of 14 hr (0.6 days) among the four cases is obtained for the $1.385\,{M}_{\odot }$ WD with a 1 yr recurrence period. In general, a nova explosion is relatively weak for a very short recurrence period, which results in a rather slow evolution toward the optical peak. This slow timescale and the predictability of very short recurrence period novae give us a chance to observe X-ray flashes of recurrent novae. In this context, we report the first attempt, using the Swift observatory, to detect an X-ray flash of the recurrent nova M31N 2008-12a (0.5 or 1 yr recurrence period), which resulted in the nondetection of X-ray emission during the period of 8 days before the optical detection. We discuss the impact of these observations on nova outburst theory. The X-ray flash is one of the last frontiers of nova studies, and its detection is essential for understanding the pre-optical-maximum phase. We encourage further observations.
DOI Link: 10.3847/0004-637X/830/1/40
ISSN: 0004-637X
eISSN: 1538-4357
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Creative Commons “Attribution Non-Commercial No Derivatives” licence CC BY-NC-ND, further details of which can be found via the following link: Archived with reference to SHERPA/RoMEO and publisher website.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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